I love playing PBBGs (persistant browser based games). There is an old (5-6+ years) game written using basic HTML/PHP that I feel like remaking using the HTML5/Javascript that I have learned.

I will also be redoing the game mechanics to take advantage of the new programming tools. E.g. HTML5 allows the webserver to push updated game states to browser without a refresh/request. And also using my own game design ideas. The name and story will also be different. But the theme and premise is basically the same.

Is this ok? Or considered unethical/plagiarism of another developer's game design?

I'll leave it to Tom Sloper to direct you to his excellent FAQ (specifically, entry #61), but as a little advance spoiler: It's not a good idea to do such a thing if you own a shirt that you're wearing.

The question is not whether it's "ethical" but whether you'll be dragged to court. If it's an obvious clone of someone's IP, and you are not totally unsuccessful and never heard of, chances aren't bad for that to happen.

In any case, abstain from using the original name or a name that sounds confusingly similar, and abstain from making something that "looks and feels" identical or nearly so. It is often "OK" to borrow some ideas as long as they are not patented (most games borrow something from somewhere), but it is never "OK" to "borrow" a name or allege a competitive product with the "original" in some way.

I don't see how this is a question of ethics or morality. Remaking or copying a game can get you sued. Making a game inspired by another game is different. You can still get sued, if you use another game's graphics or audio or code, or violate somebody's patent, copyright, or trademark. Or if someone thinks you did.

-- Tom SloperSloperama ProductionsMaking games fun and getting them done.www.sloperama.com

Please do not PM me. My email address is easy to find, but note that I do not give private advice.

I will also be redoing the game mechanics to take advantage of the new programming tools. E.g. HTML5 allows the webserver to push updated game states to browser without a refresh/request. And also using my own game design ideas. The name and story will also be different. But the theme and premise is basically the same.

Is this ok? Or considered unethical/plagiarism of another developer's game design?

IMO, from what you've said you are in relatively safe territory depending on how close you stick to the original... think of the variety of fantasy themes and sub-genres there are, for example, or how many stories start with a boy/girl that turns out to be the "chosen one". But it's always safer to inject your own ideas to move away from a direct clone, and that goes for setting, story, graphics, etc, etc.

Think of it this way: you are making a game inspired by X, not remaking X.

This topic came up just recently, where an open source copy of Terry Cavanagh's Super Hexagon was cloned (called Open Hexagon). Worst part is that the open source version beat Terry to release. The open source dev requested permission to make a game inspired by Terry's, and Terry explicitly asked for it to not be a clone. But the end result according to Terry is a clone.

no, i think this is fine as long as the game is old enough. As an example, look up to the moon on steam. Its a remake of horizons from the 80s

The mistake here is in assuming is that because someone is currently getting away with it, it's okay to do. Tom Sloper might remember a specific example, but there's been cases where the Intellectual Property rights have changed hands and hobby projects based on that IP that had previously been left alone were immediately shut down (by the new IP holders).

If you make an infringing clone, it might be days or months or years, or never before the IP holder finds you... but why take the risk when it's pretty easy (and fun) to add and change things?

Those games are nothing new to begin with. They resemble old BBS door games that existed 20-30 years ago. Legend Of The Red Dragon, Dope Wars, TradeWars, etc... LORD has even been re-implemented as an open source PBBG called LotGD (http://lotgd.net/about.php). You could start there.

I'm pretty sure if you use the same theme you'll be alright. As long as the assets are new, you don't use the same names or story, and the game has a large enough amount of unique elements to obviously distinguish itself from the inspiration.

Thanks for the input from everyone. After reading all the warnings, I have decided to distance myself from the source material and approach this project as "making a new game inspired by the old game" rather than a remake.

Yes, I intended from the beginning to use my own art assets, original name/story, 80-90% fresh mechanics. This is not a clone but more of a (for example) "Pac Man is a great game, how can I make a game with a similar concept of collecting all the dots and power-ups in a level while being chased by ghosts, enhanced by modern technology?".

As its been put by everyone else, you should be fine as long as your project is inspired by the other game, as long as you aren't taking any of the IP from the game i.e graphics, story, music, sound effects then you're safe because its just styled similar to the game that inspired the creation of your project.